Substantially rigid tubing, or pipe, such as PVC tubing is used for constructing frames of many styles. In the past there have been few, if any, acceptable connectors to permit interconnecting adjacent ends of plural tubes to hold them in desired defined angular relationships. Depending upon the strength of the tubing used, frames made of such materials could be used for various material supports, such as for supporting frames, crating or caging frame works, load support structures, etc.
Various round pipe angle connectors had been available for connecting ends of substantially rigid round tubing, but these generally have been fully open inside with little to support and limit the depth of insertion of a tube and also have generally been only for round pipe. Further they generally have provided no stop, or limit, elements which would support a rather substantial load imposed axially upon the tube.